Tissue paper products are linked by common consumer demand for a generally conflicting set of physical properties: a pleasing tactile impression (i.e.; softness) while at the same time having strength and a resistance to linting and dusting. Research and development efforts have been directed to the improvement of each of these attributes without negatively impacting the others.
Strength is the ability of the product and its constituent webs to maintain physical integrity and to resist tearing, bursting, and shredding under use conditions.
Softness is the tactile sensation perceived by the consumer as the consumer holds a particular product, rubs it across his/her skin, or crumples it within his/her hand. This tactile sensation is provided by a combination of several physical properties including the stiffness, the surface smoothness, and the lubricity of the paper web from which the product is made. Stiffness, in turn, is usually considered to be directly dependent upon the dry tensile strength of the web and the stiffness of the fibers which make up the web.
Linting and dusting refers to the tendency of a fibrous product and its constitutent web to release unbound or loosely bound fibers during handling or use. Lint resistance is the ability of the fibrous product, and its constituent web, to bind together under use conditions. In other words, the higher the lint resistance, the lower the propensity of the web to lint.
It is well known in the art that hardwood pulp fibers tend to be shorter fibers than softwood fibers. It is also well known in the art that hardwood pulp fibers tend to provide more softness and have less tensile strength than softwood pulp fibers. Additionally, it is well known that hardwood pulp fibers have more of a tendency to lint than softwood pulp fibers.
Though consumers prefer a soft tissue, transfer of lint from the tissue to the user's skin and clothing is deemed undesirable. Furthermore, a tissue, which falls apart during use by the consumer is deemed undesirable.
Hence, it would be desirable to have a tissue which is soft and exhibits resistance to lint while maintaining physical strength integrity.
U.S. Pat. No. 3,554,863 issued to Hervey et al. on Jan. 12, 1971 purports to teach a cellulose pulp sheet impregnated with a cationic long chain fatty alkyl debonding agent. Hervey et al. teaches that addition of the debonding agent reduces the tensile strength of the pulp sheet.
U.S. Pat. No. 4,144,122 issued to Emanuelson et al. on Mar. 13, 1979 purports to teach a process for treating cellulose pulp fibers to reduce interfiber bonding and impart a low degree of mechanical strength to the web formed therefrom.
In light of the prior art, one would expect to find that the addition of debonding agents to the pulp fiber increases softness while negatively impacting lint formation and the physical strength integrity of the tissue. Hence, it is unexpected to find that the present invention allows for the addition of large amounts of debonding agent to the pulp fibers to produce a soft tissue without any appreciable loss of tensile strength or increases in lint formation.
It is also unexpected to find that large amounts of debonding agent can be added to hardwood pulp to increase the softness of the tissue without a detrimental increase in lint formation and without any appreciable loss of tissue physical strength integrity. This allows for larger percentages of hardwood fibers to be utilized in the consumer contacting areas of the tissue (i.e.; outer layers and/or outer plies of the tissue).